[clang] [clang] warn_{cstruct, cxxstruct}_memaccess are too agressive about initializers (PR #170577)

[via cfe-commits]

serge-sans-paille wrote:

Thanks for the patch
!
> We could restrict this to just those targeting this inside a constructor, but I've also found cases where constructors memset/bzero subobjects?

Having a look at https://godbolt.org/z/7KThvxKx5 I'd feel better if we could capture the idiom in `ValidFoo` while still warning about `InvalidFoo`.

The scope of your patch is much larger, and it would miss several cases where it should legitimately warn.

https://github.com/llvm/llvm-project/pull/170577